Capacitor pair structure for increasing the match thereof

ABSTRACT

A capacitor pair structure for increasing the match thereof has two finger electrode structures interlacing with each other in parallel and a common electrode being between the two finger electrode structures to form a capacitor pair structure with an appropriate ratio. Also, the capacitor pair structure could further increase its entire capacitance through vias connecting the same capacitor pair structures on different metal layers.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to a capacitor pair structure, and moreparticularly, to a capacitor pair structure that increases the matchthereof.

2. Description of the Prior Art

Referring to FIG. 1A, a multi-layer stacked capacitor structure isillustrated. The first conductive layer 110 parallels to the thirdconductive layer 130 and connects to the third conductive layers 130 bya conducting wire to form an end of a multi-layer capacitor structure100. The second conductive layer 120 parallels to the fourth conductivelayer 140 and connects to the fourth conductive layer 140 by anotherconducting wire to form the other end of the multi-layer capacitorstructure 100. Herein, the second conductive layer 120 is equidistantlyinserted between the first conductive layer 110 and the third conductive130 in parallel, and the third conductive layer 130 is equidistantlyinserted between the second conductive layer 120 and the fourthconductive 140 in parallel, so that a so-called sandwich structure isformed and its capacitance in a unit volume increases through convergingstray capacitance that exists among conductive layers. However, in termsof the downside of the first conductive layer 110 and the upside of thefourth conductive layer 140, the stray capacitance is also generatedwhile other conductive layers paralleling to them, and further affectsthe operations of a circuit, especially, in high frequency. And, thequantity of the stray capacitance is a direct ratio to the areas of theconductive layers, that is, while the areas of the multi-layer stackedcapacitor structure 100 increase, not only its capacitance increases,but also the stray capacitance outside its two ends also increases.

Referring to FIG. 1B, a fringe capacitor structure is illustrated. Aplurality of conducting strips 112 and 114 are in parallel and interlaceto each other to form the first conductive layer 110, and throughappropriately connecting, the conducting strips 112 couple to adjacentconducting strips 114 to form fringe capacitors C_(f). A plurality ofconducting strips 124 and 122 are in parallel and interlace to eachother to form the second conductive layer 120, and are over and inparallel to the corresponding conducting strips 112 and 114. Throughappropriately connecting, the conducting strips 124 couple to adjacentconducting strips 122 to form fringe capacitors C_(f), in the meanwhile,the conducting strips 122 and 124 respectively couple to thecorresponding conducting strips 112 and 114 to form stray capacitorsC_(s). A plurality of conducting strips 132 and 134 are in parallel andinterlace to each other to form the third conductive layer 130, and areover and in parallel to the corresponding conducting strips 124 and 122.Through appropriately connecting, the conducting strips 132 couple toadjacent conducting strips 134 to form fringe capacitors C_(f), in themeanwhile, the conducting strips 132 and 134 respectively couple to thecorresponding conducting strips 124 and 122 to form stray capacitorsC_(s). Similarly, a plurality of conducting strips 144 and 142 are inparallel and interlace to each other to form the fourth conductive layer140 and also to form fringe capacitors C_(f), at the same time, also toform stray capacitors C_(s) between the corresponding conducting strips132 and 134. The rest conductive layers may be deduced by analogy.Finally, the maximum capacitance in a unit volume can be obtainedthrough integrating all fringe capacitors C_(f) and stray capacitorsC_(s).

The well-known capacitor structures mentioned above describe a singlecapacitor as an independent unit. However, while a circuit requires acapacitor pair application, two independent capacitors are henceconnected together. Doing in this way, it causes not only the waste ofcircuit layout, but also the instable match between the two capacitors.For example, a capacitor layout on a wafer periphery originally has afixed proportion to another capacitor layout on the wafer center.However, the fixed proportion might be changed due to the slightlydifferent thickness between the wafer periphery and the wafer center, ordue to a high current circuit layout just beside any one of thecapacitor layouts. In addition, the stray capacitance generated from theoutside of the electrodes also interferes with the capacitor pairworking in high frequency.

In view of the drawbacks mentioned with the prior art of capacitor pairstructure, there is a continued need to develop a new and improvedstructure that overcomes the disadvantages associated with the prior artof capacitor pair structure. The advantages of this invention are thatit solves the problems mentioned above.

SUMMARY OF THE INVENTION

In accordance with the present invention, a capacitor pair structure forincreasing the match thereof substantially obviates one or more of theproblems resulted from the limitations and disadvantages of the priorart mentioned in the background.

Accordingly, one object of the present invention is to provide a fringecapacitor pair structure that keeps the same capacitance as the originalvalue while the areas of the conductive layers are reduced.

Another object is to provide two finger electrode structures interlacingwith each other and a common electrode being between the two fingerelectrode structures, so as to increase the match and the layout densityof the capacitor pair.

Still another object is to provide a common electrode being between thetwo finger electrode structures interlacing with each other, so as toreduce the stray capacitance generated from the outside of the capacitorelectrodes through reducing the areas of the common electrode.

According to the aforementioned objects, the present invention providesa capacitor pair structure for increasing the match thereof. Thecapacitor pair structure includes a first finger electrode structurehaving a first electrode and a plurality of first extended electrodes,the plurality of first extended electrodes paralleling to each other andconnecting to the first electrode; a second finger electrode structurehaving a second electrode and a plurality of second extended electrodes,the plurality of second extended electrodes paralleling to each otherand connecting to the second electrode, wherein the second fingerelectrode structure interlaces with the first finger electrode structureto form an interlaced finger electrode structure; and a third electrodestructure being between the interlaced finger electrode structure.

Further scope of the applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more frilly understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

FIG. 1A illustrates a well-known multi-layer stacked capacitorstructure;

FIG. 1B illustrates a well-known fringe capacitor structure;

FIG. 2A illustrates a preferred capacitor pair structure in accordancewith the present invention;

FIG. 2B shows a practical application circuit in accordance with thepresent invention;

FIG. 3A illustrates the top view of another embodiment of the capacitorpair structure in accordance with the present invention;

FIG. 3B shows the top view of the different proportion capacitor pairstructure shown in FIG. 3A;

FIG. 4A illustrate the top view of still another embodiment of thecapacitor pair structure in accordance with the present invention; and

FIG. 4B shows the top view of the different proportion capacitor pairstructure shown in FIG. 4A.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Some embodiments of the invention will now be described in greaterdetail. Nevertheless, it should be noted that the present invention canbe practiced in a wide range of other embodiments besides thoseexplicitly described, and the scope of the present invention isexpressly not limited except as specified in the accompanying claims.

Moreover, some irrelevant details are not drawn in order to make theillustrations concise and to provide a clear description for easilyunderstanding the present invention.

Referring to FIG. 2A, a preferred capacitor pair structure in accordancewith the present invention is illustrated. A first finger electrodestructure includes a first electrode 210 and a plurality of firstextended electrodes 212, wherein the plurality of first extendedelectrodes 212 equidistantly parallel to each other and verticallyconnect to the first electrode 210. A second finger electrode structureincludes a second electrode 220 and a plurality of second extendedelectrodes 222, wherein the plurality of second extended electrodes 222equidistantly parallel to each other and vertically connect to thesecond electrode 220. The two finger electrode structures mentionedabove form a so-called interlaced finger electrode structure through thelayout of interlacing to each other. This makes the plurality of firstextended electrodes 212 be equidistantly and in parallel interlacedamong the plurality of first extended electrodes 222 respectively. Athird electrode structure 230 equidistantly zigzags between theinterlaced finger electrode structure formed by the first fingerelectrode structure and the second finger electrode structure, so as toform two capacitor structures with the same capacitance between thefirst finger electrode structure and the third electrode structure 230,and between the second finger electrode structure and the thirdelectrode structure 230. The capacitance depends on fringe capacitancegenerated between electrode structures.

In the present embodiment described above, the sizes of the two fingerelectrode structures are the same, and the coupled areas of the twofinger electrode structures to the third electrode structure 230 arealso the same. Therefore, the proportion of the two capacitors is 1:1.Moreover, when the effects are generated by external factors, such asdifferent wafer thickness or different density circuit layout beside,the changed ranges of the two capacitors are the same and thecapacitance proportion is kept at a fixed value due to the interlacedlayout. Also, the interlaced layout and fringe capacitor effectsemployed by the present embodiment not only keep the originalcapacitance after the areas of the circuit layout being reduced, butalso reduce the stray capacitance generated from the outside of theelectrodes. Besides, the first finger electrode structure, the secondfinger electrode structure, and the third electrode structure 230 couldrespectively connect to the same electrode structures on differentconductive layers through a plurality of first vias 214, a plurality ofsecond vias 224, and a plurality of third vias 234 to increase thecapacitance of the capacitor pair by utilizing the stray capacitancegenerated between the same electrode structures of different conductivelayers.

Referring to FIG. 2B, a practical switched-capacitor circuit inaccordance with the present invention is illustrated. A contact B is thecommon contact of a capacitor C1, a capacitor C2, and one input of anelectric device 250, such as an operation amplifier. The contact B couldbe the third electrode structure shown in FIG. 2A, and a contact A and acontact C could be respectively the first finger electrode structure 210and the second finger electrode structure 220. From the circuit aspect,the stray capacitance between the contact B and the ground is as smalleras better, so that the noise will not be directly coupled from theground via contact B while the circuit works in high frequency. Thecapacitor pair structure in accordance with the present inventionreduces a traditional flat common electrode to a zigzagged commonelectrode, such as the third electrode structure 230 shown in FIG. 2A,zigzagging between two interlaced finger electrode structures. Hence,the stray capacitance between the zigzagged common electrode and theground is also reduced under ⅓ original capacitance. Besides, thecapacitor C1 and the capacitor C2 in the present invention can keep afixed proportion and good match.

Referring to FIG. 3A, another preferred capacitor pair structure inaccordance with the present invention is illustrated. A first fingerelectrode structure includes a first electrode 310 and a plurality offirst extended electrodes 312, wherein the plurality of first extendedelectrodes 312 equidistantly parallel to each other and verticallyconnect to the first electrode 310. A second finger electrode structureincludes a second electrode 320 and a plurality of second extendedelectrodes 322, wherein the plurality of second extended electrodes 322equidistantly parallel to each other and vertically connect to thesecond electrode 320. The two finger electrode structures mentionedabove form a so-called interlaced finger electrode structure through thelayout of interlacing to each other. This makes the plurality of firstextended electrodes 312 be equidistantly and in parallel interlacedamong the plurality of first extended electrodes 322 respectively. Athird electrode structure includes a fourth electrode 330 and aplurality of third electrodes 332, wherein the plurality of thirdelectrodes 332 equidistantly parallel to each other, equidistantlyinterlacing between the plurality of first extended electrodes 312 andthe plurality of second extended electrodes 322 respectively, andconnect to the fourth electrode 330 through a plurality of third vias334, and the fourth electrode 330 could be position on differentconductive layer. A guard dummy structure 340 surrounds the first fingerelectrode structure, the second finger electrode structure, and theplurality of the third electrodes 332 to isolate the noise outside. Forexample, the sensed capacitance of the capacitor pair from an adjacenthigh density circuit could be reduced by the guard dummy structure 340.This increases the accuracy of the capacitance of the present capacitorpair.

In the present embodiment described above, the sizes of the two fingerelectrode structures are the same, and the coupled areas of the twofinger electrode structures to the plurality of third electrodes 332 arealso the same. Therefore, the proportion of the two capacitors is still1:1. Similarly, the first finger electrode structure, the second fingerelectrode structure, and the plurality of third electrodes 332 couldrespectively connect to the same electrode structures on differentconductive layers through a plurality of first vias 314, a plurality ofsecond vias 324, and the plurality of third vias 334 to increase thecapacitance of the capacitor pair by employing the stray capacitancegenerated between the same electrode structures of different conductivelayers.

Referring to FIG. 3B, a capacitor pair structure with differentproportion modified from the capacitor pair structure shown in FIG. 3Ais illustrated. The main difference between the capacitor pair structureshown in FIG. 3B and the capacitor pair structure shown in FIG. 3A isthat a plurality of second extended electrodes 322 have no the samelengths to a plurality of first extended electrodes 312, so that thefringe capacitance between the plurality of second extended electrodes322 and a plurality of third electrodes 332 is not equal to the fringecapacitance between the plurality of first extended electrodes 312 andthe plurality of third electrodes 332. The proportion of the capacitorpair depends on the length proportion of the plurality of first extendedelectrodes 312 to the plurality of second extended electrodes 322. Thatis, any capacitance proportion for the capacitor pair structure can beobtained through adjusting the length proportion of the plurality offirst extended electrodes 312 to the plurality of second extendedelectrodes 322. For example, while the length proportion of theplurality of first extended electrodes 312 to the plurality of secondextended electrodes 322 is 1:0.75 or 0.75:1, the proportion of thecapacitor pair is respectively 1:0.75 or 0.75:1. A plurality of dummyextended electrodes 350 compensate the lengths of a plurality of shorterextended electrodes, but do not connect to the plurality of shorterextended electrodes, wherein the plurality of shorter extendedelectrodes could be the plurality of first extended electrodes 312, andalso could be the plurality of second extended electrodes 322. By doingso, the defect status on both ends resulted from the space withoutlayouts can be avoided. For example, a crooked extended electrode in themanufacture process causes inaccurate capacitance.

Referring to FIG. 4A, still another preferred capacitor pair structurein accordance with the present invention is illustrated. A first fingerelectrode structure includes a first electrode 410 and a plurality offirst extended electrodes 412, wherein each the plurality of firstextended electrodes 412 has a first end and a second end, and theplurality of first extended electrodes 412 equidistantly parallel toeach other and vertically connect to the first electrode 410 with theplurality of first ends. A second finger electrode structure includes asecond electrode 420 and a plurality of second extended electrodes 422,wherein each the plurality of second extended electrodes 422 has a thirdend and a fourth end, and the plurality of second extended electrodes422 equidistantly parallel to each other and vertically connect to thesecond electrode 420 with the plurality of third ends. The plurality ofsecond ends are horizontally in opposition to the plurality of thirdends. This makes the first finger electrode structure and the secondfinger electrode structure form an opposite finger structure. A thirdelectrode structure includes a fourth electrode 430 and a plurality ofthird electrodes 432, wherein the plurality of third electrodes 432equidistantly parallel to each other, connecting to the fourth electrode430 through a plurality of third vias 434 and, their two endsequidistantly interlace between the plurality of first extendedelectrodes 412 and between the plurality of second extended electrodes422 respectively, and the fourth electrode 430 could be position ondifferent conductive layer. A guard dummy structure 440 surrounds thefirst finger electrode structure, the second finger electrode structure,and the plurality of the third electrodes 432 to isolate the noiseoutside.

In the present embodiment described above, since the fourth electrode430 on a different conductive layer has no perpendicularly overlappedareas over the plurality of first extended electrodes 412 and theplurality of second extended electrodes 422, the stray capacitancebetween the fourth electrode 430 and the extended electrodes cannot begenerate to affect the accuracy of the capacitance. Also, the sizes ofthe two finger electrode structures are the same, and the coupled areasof the two finger electrode structures to the plurality of thirdelectrodes 432 are also the same. Therefore, the proportion of the twocapacitors is still 1:1. Likewise, the first finger electrode structure,the second finger electrode structure, and the plurality of thirdelectrodes 432 could respectively connect to the same electrodestructures on different conductive layers through a plurality of firstvias 414, a plurality of second vias 424, and the plurality of thirdvias 434 to increase the capacitance of the capacitor pair.

Referring to FIG. 4B, a capacitor pair structure with differentproportion modified from the capacitor pair structure shown in FIG. 4Ais illustrated. The main difference between the capacitor pair structureshown in FIG. 4B and the capacitor pair structure shown in FIG. 4A isthat a plurality of second extended electrodes 422 have no the samelengths to a plurality of first extended electrodes 412, so that thefringe capacitance between the plurality of second extended electrodes422 and a plurality of third electrodes 432 is not equal to the fringecapacitance between the plurality of first extended electrodes 412 andthe plurality of third electrodes 432. Likewise, the proportion of thecapacitor pair depends on the length proportion of the plurality offirst extended electrodes 412 to the plurality of second extendedelectrodes 422. That is, any capacitance proportion of the capacitorpair structure can be acquired via adjusting the length proportion ofthe plurality of first extended electrodes 412 to the plurality ofsecond extended electrodes 422.

However, in addition to the above-mentioned disclosures, which changethe proportion of the capacitor pair by changing the lengths of theextended electrodes, the proportion of the capacitor pair can be changedthrough the vias to appropriately connect the same electrode structuresof different conductive layers. For example, referring to FIG. 3A again,the first electrode structure and the second electrode structure havethe same size, and the fringe capacitance between two of them to theplurality of third electrodes 332 are also the same, so the proportionof the capacitor pair is 1:1. However, while the first electrode and theplurality of third electrodes 332 respectively connect to the sameelectrode structures on other conductive layers by the plurality offirst vias 314 and the plurality of third vias 334, yet the secondelectrode structure still keeps the fringe capacitance on the singleconductive layer, the proportion of the capacitor is then changed to 2:1or above 2:1. That is, while the same electrode structures on differentconductive layer do not overlap with the present electrode structures,the proportion of the capacitor is 2:1 since the capacitance onlyincreases the fringe capacitance of the same electrode structures on thedifferent conductive layer. On the other hand, while the same electrodestructures on different conductive layer overlap with the presentelectrode structures, the proportion of the capacitor is above 2:1 sincethe capacitance increases not only the fringe capacitance of the sameelectrode structures on the different conductive layer, but also thestray capacitance between the present electrode structures and the sameelectrode structures on the different conductive layer. Through suitablycalculating and connecting by vias, the capacitor pair structures shownin FIG. 3A and FIG. 4A can have different proportions to meet thepractical needs. Likewise, the connection approach also can be utilizedin the capacitor pair structures shown in FIG. 3B and FIG. 4B to obtainthe higher capacitance.

Although specific embodiments have been illustrated and described, itwill be obvious to those skilled in the art that various modificationsmay be made without departing from what is intended to be limited solelyby the appended claims.

1. A capacitor pair structure for increasing the match thereof, saidcapacitor pair structure comprising: a first finger electrode structurehaving a first electrode and a plurality of first extended electrodes,said plurality of first extended electrodes being parallel to each otherand connecting to said first electrode; a second finger electrodestructure having a second electrode and a plurality of second extendedelectrodes, said plurality of second extended electrodes being parallelto each other and connecting to said second electrode, wherein saidsecond finger electrode structure is interlaced with said first fingerelectrode structure; a third electrode structure having a plurality ofthird electrodes located on an interconnect level, wherein saidplurality of third electrodes are physically separate from each otherand are not connected on the same interconnect level, and arerespectively interlaced between said first finger electrode structureand said second finger electrode structure; and a fourth electrodeconnected to said plurality of third electrodes by a plurality of vias,said fourth electrode having a single conductive strip with an elongatedrectangular shape and being located on an adjacent interconnect leveldifferent from the interconnect level of said plurality of thirdelectrodes; wherein the adjacent interconnect level includes said fourthelectrode, but excludes said first finger electrode structure, saidsecond finger electrode structure and said plurality of thirdelectrodes.
 2. The capacitor pair structure according to claim 1,wherein said plurality of first extended electrodes are equidistant toeach other, said plurality of second extended electrodes are equidistantto each other, and said plurality of third electrodes are equidistant toeach other.
 3. The capacitor pair structure according to claim 1,wherein said plurality of first extended electrodes perpendicularlyconnect to said first electrode, and said plurality of second extendedelectrodes perpendicularly connect to said second electrode.
 4. Thecapacitor pair structure according to claim 1, wherein said plurality ofthird electrodes are respectively equidistantly interlaced between saidfirst finger electrode structure and said second finger electrodestructure.
 5. The capacitor pair structure according to claim 1, whereinsaid plurality of first extended electrodes are shorter than saidplurality of second extended electrodes, a plurality of dummy extendedelectrodes are utilized to compensate lengths of said plurality of firstextended electrodes, said plurality of dummy extended electrodes do notconnect to said plurality of first extended electrodes.
 6. The capacitorpair structure according to claim 1, further comprising a guard dummystructure, wherein said guard dummy structure surrounds said firstfinger electrode structure, said second finger electrode structure, andsaid third electrode structure.
 7. The capacitor pair structureaccording to claim 1, wherein said first finger electrode structure canconnect to another first finger electrode structure on anotherconductive layer by a plurality of first vias, said second fingerelectrode structure can connect to another second finger electrodestructure on another conductive layer by a plurality of second vias,said third electrode structure can connect to another third electrodestructure on another conductive layer by a plurality of third vias.